Electron discharge device employing resonators



Jan. 3 HQSQ v, HAEFF 2,492,987

ELECTRON DISCHARGE DEVICE EMPLOYING RESONATORS Original Filed July 25, 1942 3 Sheets-Sheet l INENTOR ATTORNE Y Jan, 3, 950 A. v. HAEFF ELECTRON DISCHARGE DEVICE EMPLOYING RESONATORS 3 Sheets-Sheet 2 Original Filed July 25, 1942 VENTOR By w ATTORNEY; i

A. v. HAEFF 2 49238? ELECTRON DISCHARGE DEVICE EMPLOIING RESONATORS 3 Sheets-Sheet 3 Jan. 3, 195% Original Filed July 25, 1942 5 125' 120 we .1. #9 1/1 4 34; m 77 P152 7 BY a A; WMTOR' W l atented Jan. 3, 1950 UNITED STATES ram" OFFICE ELECTRON DISCHARGE DEVICE EMPLOY- ING RESONATORS Andrew V. Haefl, Washington, D. 0., .assignor to Radio Corporation of America, a corporation,

of Delaware 4 Claims.

My invention relates to electron discharge devices and associated circuits particularly suitable for ultra high frequencies as high power output tubes which are useful as amplifiers or oscillators.

The present application is a division of my copending application, Serial No. 452,302 filed July 25, 1942, now Patent No. 2,400,753, dated May 21, 1946., and assigned to the same assignee as the present application.

The electron discharge devices intended for high power output and particularly for use at ultra high frequencies, close spacing of the electrodes and high operating voltages are requisites. ()ptimum operating conditions for maximum output require a maximum instant grid voltage and a minimum instant plate voltage when the peak plate current flows. However, for the usual electron discharge device undesired grid emission due to electron bombardment from the cathode and heating of the grid by radiated heat from the electron collecting surface of the anode or .collector may result. Grid and plate circuitloading, burning out of the grid and increased heating at the anode, which represents wasted energy and hence a lowering of the eificiency of the electron discharge device, may occur under these conditions.

In the case of oscillators either self-biasing resistors may be used or fixed bias maybe used to obtain the proper biasing voltage on the grid. Where a self-biasing resistor is used between grid and cathode, when the grid is positive, electrons strike the grid and cause secondary emission, which results in current fiowing in the grid circuit. This results in a higher positive bias being placed on the grid, thus further increasing the positive grid potential and the velocity of the electrons bombarding the grid. This building up of the positive bias on the grid may cause the grid to burn out.

In the case of a fixed bias, While the bias itself does not increase, nevertheless when the grid is at positive peak and plate voltage is at a minimum positive voltage, electrons striking the grid cause it to heat up, thus causing emission from the grid. Electrons emitted from the grid during the next half cycle, when the grid is negative and the anodepositive, cause the electrons from the grid to be accelerated toward the anode with maximum' velocity. These high velocity electrons strike the anode with considerable force and dissipate their energy in heat. Thus energy is wasted and does not go into the output as useful energy. This grid emission current, of course,

.2 also loads down the plate circuit, another undesirable factor.

fIIlpOldfil to minimize gridemission, lower peak gridv voltages are required, which as pointed, out above means higher plate voltages with ..lower plate efiiciency. .It is desirable to have the electrons collected by the plate at a low velocity and to remove the electron receiving surface away from the grid to reduce heatabsorbed by the grid. But withv the usual, three-electrode arrangement with the collector anode at a high positive voltage in order to draw the necessary. plate current, this is not entirely feasible.

..It is, -therefore,.,an object of my invention to provide an electron discharge device having a high power output and which is suitable for use at ultra high frequencies as an amplifier or oscillator.

More specifically, it is another object of my invention to provide an electron discharge device in which grid emission is substantially reduced.

-A still further object of my invention is to provide an electron discharge device in which the electrons maybe collected ata lowvelocity to re-,

duce the energy dissipated in heat.

These and other objects will appear hereinafter.

The novel features which I believe to be characteristic .of my invention are set forth with particularity inthe appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawing inwhich Figure lis alongitudinal section of an electron discharge device and associated circuit made according .to myinvention and Figures. 2, 3, 4and 5'show longitudlnalsections of modifications of the electron discharge device show-11in Figure '1.

In Figure 1 I providean apparatus which can be used as a highpower triode amplifieror as an oscillator. It includes an indirectly heated cathode ll! followed'byagrid ll andan-anode orcollector;.|2,having coolingfins 12'. The envelope is formed by means of the conducting collarmember I3 closed at one end by the cup-shaped insulating member I4 and at its other end by the insulating collar member 15 and collector 1.2 pro vided with the collar member zl sealed to the collar I5. The cathode heater H) is provided with a,lead .ldextending through the envelope. The cathode i0 is supported by means of theconductors and leads l8 arranged in a circle around-conductor I6 and secured at one end to the tubular member H, the other end of the tubular member I] being secured to the leads 19' extending through the envelope. Members |1, l8 and 9 serve as the other lead for the cathode heater and as the cathode lead. Insulating disc properly centers conductor IS with respect to tubular member ii. The grid II is supported by means of conducting collar member 2| secured to the tubular conducting member l3 forming part of the tube envelope, the grid and cathode supports being separated by means of the insulating disc 22. The collector |2 is provided with the member decreasing in diameter toward the grid to protect the seal and provide a proper field for the electrons. Across the opening is placed the wire mesh 26 for bringing about the proper field formation through which the electrons pass from the grid to the interior of the collector l2. This has the efiect of minimizing effective transit time between grid and anode.

The input circuit connected between the grid and cathode comprises the outer tubular member 28 electrically connected to the collar member l3 and an inner tubular member 29 capacity coupled at its inner end to the element 32 contacted by the spring-like elements 39 secured to.

the cathode leads. The member 32 electrically connected to the elements provides one conductor through which the heating current flows to the cathode heater. The inner conductor i6 is engaged by means of a spring clip member 34 positioned on element 33 capacity coupled to element 32. This arrangement provides means through which the cathode direct current flows to the heater and at the same time provides a path for radio frequency currents. It will thus be observed that the grid collar 2|, collar i3, member 28, member 29, capacity coupling element 32, leads 3B and i9, tubular member I"! and leads l8 provide a coaxial line type resonator cavity circuit completely isolated from other circuits. It is tuned by means of the collar-like element 35 slidably supported on the inner tubular member 29 by means of the insulator support 35'.

The output circuit includes a drum-like member 36 electrically connected to collar |3 of the envelope and provided with a disc-like element 31 capacity coupled to the disc-like element 38 positioned transversely of the collar member 21 of the collector i2 and electrically connected thereto. Energy from the output tank circuit is coupled back to the input circuit by means of the coaxial transmission line comprising inner conductor 39 and outer conductor 40. This lineis made adjustable to insure proper phase relationship of the energy feedback with respect to the voltages in the input circuit, the inner conductor being provided with coupling loops 4| and 42. This adjustable transmission line is described in greater detail and claimed in my copending application Serial No. 455,175, filed August 18, 1942 now Patent No. 2,440,089, dated April 20, 1948 and assigned to the same assignee as the present application. These coupling loops could be made adjustable to control the amount of feedback. This arrangement permits both the input and output circuits to be adjusted independently of each other and for optimum operating conditions. The output is taken by means of loop 46 which feeds into the coaxial transmission line 41.

The transformer 43 supplies heating current for the cathode heater, and resistor 44 provides the biasing voltage between the grid and cathode. The anode or collector voltage is supplied by means of voltage source 45.

In operation an alternating high frequency voltage applied between the grid II and cathode i0 modulates the electron stream passing to the collector i2. The modulated. electron stream in passing across the gap between the grid and the surface of the mesh closure member 25 induces a voltage in the resonant cavity 36 coupled between the grid and the collector, thus energizing this resonant cavity circuit. Energy is then fed back by means of coupling loop 4|, transmission line 3940 and coupling loop 42 within the coaxial transmission line acting as the input resonant cavity circuit and comprising members 28 and 29. Tuning of the input circuit is accomplished by means of the tuning collar 35 which may be moved longitudinally of the input circuit. Output may be taken from the resonator 36 by means of the coupling loop 46 and coaxial transmission line 47. In order to feed the energy from the output resonator to the input resonant cavity circuit in proper phase, the length of the transmission line 3949 may be varied by varying the position of the movable U-shaped element 40' of this line to increase or decrease the length of the line.

In the apparatus shown in Figure 1, the input and output circuits are completely isolated from each other. Due to the fact that electrons are collected at a surface far removed from the grid little radiated heat is absorbed by the grid. This eliminates much of the difiiculty due to grid emission caused by absorption of heat due to the energy dissipated at the surface of the collector. The large collar-like support 2| for the grid acts as a means for conducting heat away from the grid rapidly to thus further maintain the grid at a low temperature. In efiect close spacing of the electrodes is obtained by means of the structure shown without actually placing the collecting surface close to the grid, thus making the device suitable for use at ultra high frequencies where transit time between the electrodes becomes important. The capacity coupling between the output circuit and the anode or collector permits different voltages to be applied to the circuit and the collector and yet at the same time provides a resonant cavity type of circuit which is particularly suitable for use at ultra high frequencies. The apparatus shown in Figure 1 can be used either as an amplifier or oscillator by controlling the amount and phase of the energy fed into the input circuit,

In Figure 2 is shown a modification of the device shown in Figure l and employing ring type seals. The modification shown in this figure has an added advantage in that the collector may be maintained at a low voltage with respect to some other electrodes within the tube so that the electrons can be collected at a lower velocity than is possible in the apparatus shown in Figure 1, thus further increasing the efliciency of the tube.

The envelope 59 contains an indirectly heated cathode 5|, grid 52, output and accelerator electrode 53, ring-like secondary electron suppressor 54 and cup-shaped collector 55. The cathode, grid and accelerator electrodes are supported by means of ring members 56, 51 and 58 sealed through the glass envelope. These ring members provide low loss, low inductance leads for the electrodes and merge into the circuits utilized with the device.

The input circuit comprises a flat-drum-like member 60 electrically connected to the ring 51 and capacitively coupled to the cathode ring 56 by means of the disc-like member 56' electrically a ea-9t connected to the cathode ring 56. The output resonant cavity comprises the drum-like member 5| having .a wall 62 capacitively coupled to the flat disc-like element 63 electrically connected to the accelerator electrode ring 58. The two circuits are coupled by means of a transmission line formed by an annular shaped member 64 surrounding the input circuit. Within member 64 is supported the inner conductor 85 having coupling loop 66 positioned within the input circuit and a coupling loop 81 positioned in the output circuit. This transmission line permits ineffect a long line occupying a small space.

Cathode heating energy is supplied by means of the transformer 68 and the grid biasing voltage supplied by means of the dropping resistor 69. The collector electrode and suppressor electrode voltages are supplied by means of the voltage source 10, the suppressor being at the lower potential. The output is taken in the usual way by loop BI,

With the arrangement shown the accelerator electrode 53 is maintained at a high potential sufiicient to draw a large cathode current. Practically no current is drawn by the accelerator 53 so that little energy is dissipated in this electrode. Collector which is outside the radio frequency circuit may be maintained at a lower potential than would be the case if it acted as an output electrode and hence electrons are collected at a lower velocity so that energy wasted as heat is reduced. The input and output circuits are completely isolated from each other and the amount of feedback can be controlled as well as its phase by means of the transmission line which can be made adjustable.

In the apparatus shown in Figure 2 an alternating high frequency voltage applied between cathode 5I and grid 52 modulates the electron stream from cathode 5| and which passes to the accelerator and output electrode 53 and is collected bycollector 55, secondaries from 55 being suppressed by electrode 54. The modulated electron stream in passing across the gap between grid 52 and accelerator 53 induces a voltage across the gap, causing energization of the resonator BI. The accelerator 53 is capacitively coupled by means of the element 58 and wall 62 of resonator 6!, the radio frequency field being confined within this resonator. The collector, therefore, is external to the radio frequency circuit. The input resonant cavity circuit comprises resonator 83 electrically connected to the grid 52 through collar 51 and capacitively coupled for radio frequency to the cathode by means of elements 50' and the radially directed ring-like conducting support 56 of the cathode 5|. Energy is fed back into the input circuit by means of the transmission line comprising the loop 61, coil 65 within the annular box-shaped arrangement 64 and loop 60 within the input resonator. This causes the, device to operate as an oscillator.

In Figure 3 is shown a further modification of the construction shown in Figure 2 and provided further with an adjustable transmission line for controlling the phase of feedback. In this modification the envelope 15 contains the indirectly heated cathode '55, grid ll, output and accelerator electrode 78, suppressor electrode 19 and collector 80, the cathode heater being supplied through the conductor 8! and conductors 82 mounted in a'circle and surrounding the conductor BI and serving as a support for the cathode. The grid is supported on collar 83, which in turn is supportedon leads and support wires 84 mounted in .a circle-and surrounding conductors .82 and extending through the envelope'of the tube. The accelerating electrode is supported by means of radially directed collar 85 connected to and supported by the radially directed ring-like conductor 85 extending through the envelope.

The input circuit comprises the outer tubular member 81 electrically connected to the inner tubular member 88 by means of the closure member .9I. The inner tubular member 88 is capacitively coupled to the collar 89 secured to the outer end of the leads and supports 82, the insulating coilar'90 serving to separate members 88 and 89. "The input circuit may be tuned by a-member 92 slidable longitudinally of the input circuit.

The output tankcircuit includes the resonant cavity structure comprising the member 93 and having one wall 84 provided with an outside annular member 95 in which the conducting disc 96 is supported "by means of insulating discs --9'I anad 98. This disc is provided with springcontactengaging members 09 contacting member 86. This construction permits the envelope to be withdrawn from the output tank circuit anddisengaged therefrom. Another wall I of the resonant cavity is supplied with spring contact members IIII engaging the conductors supporting the grid. The cathode heating circuit includes transformer I06 connected to leads 8| and 82 by-spring contact members BI and .82; Voltage source I08 supplies accelerator electrode :18 maintained at a higher potential, than the collector bymeans of voltage source I09. Thus, the envelope and its electrodes. may be disengaged from the circuits by pulling the envelope to the right.

Energy may be returned to the input circuit to neutralize .input losses or cause the tube to function as an oscillator by means of the transmission line having inner conductor I and outer conductor I02, one end being .provided with coupling loop I03 and the other with coupling loop I04. Intermediate the concentric transmission 45 line is a U-shaped adjustable portion comprising the conductors I05 and I02, which are telescopically engaged with the coaxial line. Thus, by varying the length of this line the phase relationship of the energy fed back from the out- 60 put circuit to the input circuit can be controlled to insure the desired phase relationship. The output is taken by means of coupling loop H0.

Otherwise the apparatus functions in a manner similar to that shown in Figure 2.

In Figures 4 and 5 are shown modifications of the constructions shown in Figure 3 in which the outside condenser coupling arrangement for the accelerator is avoided. In the arrangement shown in Figure 4 the envelope IIO encloses the 0 cathode III, control grid II2, accelerator'and output-electrode I I3, and collector I I5 having a mesh conductor IIG positioned across the opening for providing the proper field between the electrodes. The cathode III is provided with an inner heater, conductor II! and outer conductors and leads II8 surrounding conductor III, the input circuit being provided by means of the tubular member I20 capacitively coupled to the outer tubular member I2I by means of the collar I23 having a supporting disc I23 connected between it and the inner tubular member I20. Member I2I is connected to grid leads H2" connected to collar 2' of grid H2.

The output electrode H3 is provided witha radially extending supporting and conducting member II4 electrically connected to the disc I 26 closing one end of the tubular member I 24 which is closed at the other end by means of the disc I25 to provide the output tank circuit of the resonator type connected between the grid and output electrode. The output circuit is energized in the usual way by inductive eifect when the modulated stream of electrons passes across the gap between grid H2 and output electrode II3.

The collector voltage is supplied by means of voltage source I35.

Thus the electrode I I3, which is maintained at control grid potential serves to minimize capaci tance between the control grid and collector. Large capacitance between the collector and electrode II3 serves to bypass radio frequency currents. The electron collecting area of the collector is far removed from the control grid and cathode so that the grid may be run quite cool.

In Figure 5 is shown another arrangement in which the collector may be maintained at a lower positive potential than the output electrode or accelerator. A separate high positively biased electrode is used to get high peak currents. This electrode does not take current. The collector is outside of the radio frequency circuit and has a potential applied only sufiicient to collect the electrons. Thus, there results a high eficiency apparatus of the kind shown in Figure 3, but without the need of an external capacity coupling arrangement.

In this arrangement the envelope I contains the cathode I50, and grid I supported on collar I6I. The screening and shielding electrode I62 is supported by the radially extending support and lead arrangement, I63 which extends through the wall of the envelope. The collector I64 is positioned to receive electrons from the cathode, the accelerator I65 being positioned within the screen electrode I62.

The input circuit comprises the outer tubular conductor I10 connected to the grid leads and supports I6I' and the inner tubular member I1I which is connected to the cathode leads and support I69. The output circuit comprises the resonant cavity circuit I61 having a wall I65 electrically connected to the radial leads I63 and another wall I66 electrically connected to the tubular member I10. The two circuits are coupled by means of the coupling loop I12. Cathode heating current is supplied by means of transformer I14 through lead I68 and leads I69 and grid bias voltage by means of voltage source I13. The accelerator and collector voltages are supplied by potential sources I16 and I11. The output is taken by coupling loop I80.

In the last arrangement described the collector is maintained at a lower potential than the accelerator.

High frequency apparatus made according to my invention eliminates or substantially reduces aim-ea the difliculties due to grid emission. Efllciency is increased by providing means for collecting the electrons at low velocity. This is accomplished while at the same time providing high power outputs whether the apparatus is used as an amplifier or oscillator. My apparatus also provides a ready means for disconnecting the electrodes from the associated circuits, thus making available an electron discharge device and an associated circuit apparatus permitting ready replacement in case of damage to the tube or where replacement is desired for other reasons.

While I have indicated the preferred embodiments of my invention of which I am now aware and have also indicated only one specific application for which my invention may be employed, it will be apparent that my invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without departing from the scope of my invention as set forth in the appended claims.

What I claim as new is:

1. An electron discharge device having an envelope containing a cathode for supplying electrons, a control grid electrode and another electrode in the order named, a conductor supporting said cathode and extending through said envelope, said control grid electrode having a conducting and supporting means extending through said envelope, a cavity resonator sur rounding said envelope and coupled between said control grid electrode and said other electrode,

: and including a conducting member coaxial with said control grid electrode and coupled to said conducting and supporting means adjacent the outside wall of said envelope, said conducting and supporting means forming a continuation of the wall of said cavity resonator, and a cathodegrid resonator coupled between said cathode and grid.

2. An electron discharge device having an envelope containing a cathode having conducting and supporting means extending through the envelope, :3, grid electrode shielding said cathode electrode and having conducting and supporting means extending externally of the envelope, an output electrode positioned adjacent the grid electrode but spaced therefrom to provide a gap and conducting means extending radially from the output electrode, said radially extending means extending outside the wall of the envelope, a cavity resonator electrically connected to the grid conducting and supporting means and having a wall including an element capacitively coupled to the wall of the cavity resonator, said element having resilient contacting fingers contacting the radially extending conducting means on said output electrode and other contacting fingers on said cavity resonator electrically connecting the cavity resonator to said grid conducting and supporting means and an input circuit comprising a coaxial line electrically connected to the grid electrode and capacitively coupled to the cathode, and a coaxial transmission line electrically coupled between the cavity resonator and the input circuit.

3. An electron discharge device having an envelope containing a cathode having conducting and supporting means extending through the envelope, a grid electrode having conducting and supporting means extending externally of the envelope, an output electrode positioned adjacent the grid electrode but spaced therefrom to provide a gap and conducting means extending from the output electrode and outside the wall of the envelope, a cavity resonator electrically connected to the grid conducting and supporting means and having a wall including an element capacitively coupled to the wall of the cavity resonator, said element having resilient contacting fingers contacting the conducting means on said output electrode and other contacting fingers on said cavity resonator electrically connecting the cavity resonator to said grid conducting and supporting means and an input circuit connected to the grid electrode and capacitively coupled to the cathode.

4. An electron discharge device having an envelope containing a cathode having conducting and supporting means extending through the envelope, a grid electrode shielding said cathode electrode and having conducting and supporting means extending externally of the envelope, an output electrode positioned adjacent the grid electrode and spaced therefrom to provide a gap, and having conducting means extending radially to the outside of the envelope, a cavity resonator having a wall including an element capacitively coupled to the wall of the cavity resonator, said element having resilient contacting fingers contacting the radially extending conducting means of the output electrode on the outside of said envelope, and other contacting fingers on said cavity resonator electrically connecting the resonator to said grid electrode conducting and supporting means, and an input circuit electrically connected to the grid electrode and capacitively coupled to the cathode, and a transmission line electrically coupled between the cavity resonator and the input circuit.

ANDREW V. HAEFF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,284,405 McArthur May 26, 1942 2,408,355 Turner Sept. 24, 1946 2,416,565 Beggs Feb. 25, 1947 2,425,748 Llewellyn Aug. 19, 1947 

